On Sun, Feb 05, 2023 at 02:13:42PM +0000, Jonathan Cameron wrote: > > On Sun, 5 Feb 2023 11:12:23 +0100 > Philippe De Muyter <phdm@xxxxxxx> wrote: > > > I use the imu/st_lsm6dsx (i2c) driver to drive a ism330dlc imu. > > > > Every time I start a new acquisition of gyro values, the first two > > values read are wrong, as can be see here : > > > > So, some random thoughts on what might be going on... > 1) Stale data in the fifo. Could you run this experiment twice whilst being > careful not to move the device between the runs. If we still see the wrong > values at the start then it's not that... Here are the results (I have enabled by hand the three in_anglvel channels) # while true; do sudo iio/iio_generic_buffer -n ism330dlc_gyro -g -c 6 -a; sleep 2; done iio device number being used is 1 trigger-less mode selected Auto-channels selected but some channels are already activated in sysfs Proceeding without activating any channels -0.133416 -0.916011 0.466650 -0.014382 -0.360774 0.140454 -0.000612 -0.076653 0.035190 -0.000459 -0.076347 0.035496 -0.000306 -0.076347 0.035037 -0.000612 -0.076347 0.035037 iio device number being used is 1 trigger-less mode selected Auto-channels selected but some channels are already activated in sysfs Proceeding without activating any channels -0.134640 -0.911880 0.467415 -0.013923 -0.361233 0.142443 -0.000765 -0.076041 0.035496 -0.000459 -0.076041 0.035190 -0.000306 -0.076347 0.035343 -0.000612 -0.076347 0.035343 iio device number being used is 1 trigger-less mode selected Auto-channels selected but some channels are already activated in sysfs Proceeding without activating any channels -0.137853 -0.912645 0.468792 -0.013770 -0.361233 0.142443 -0.000153 -0.076500 0.035190 -0.000306 -0.076347 0.035190 -0.000306 -0.076194 0.035190 -0.000153 -0.076194 0.035343 iio device number being used is 1 trigger-less mode selected Auto-channels selected but some channels are already activated in sysfs Proceeding without activating any channels -0.136017 -0.914787 0.467874 -0.014229 -0.361080 0.142290 -0.000153 -0.076500 0.035649 0.000918 -0.076347 0.039933 0.000306 -0.076500 0.038556 0.000459 -0.076194 0.036414 iio device number being used is 1 trigger-less mode selected Auto-channels selected but some channels are already activated in sysfs Proceeding without activating any channels -0.133722 -0.914787 0.469710 -0.013617 -0.361386 0.142290 -0.000459 -0.076347 0.035037 -0.000459 -0.076194 0.035190 -0.000459 -0.075888 0.035037 -0.000612 -0.076347 0.035649 iio device number being used is 1 trigger-less mode selected Auto-channels selected but some channels are already activated in sysfs Proceeding without activating any channels -0.135711 -0.915399 0.468792 -0.013923 -0.360927 0.142137 -0.000459 -0.076347 0.035343 -0.000459 -0.076194 0.035190 -0.000306 -0.076041 0.035496 -0.000459 -0.075888 0.035190 ^C > > 2) Device takes a little whilst to stabilize. Possibly this is down to the > low pass filters requiring a few samples before they deliver stable output. > From a quick glance I don't think we provide any userspace control of those > filters and I think LPR1 is left in default state of disabled. > > You could try messing with the sampling frequency as that may affect the number > of bad samples you see and give us more of a clue (it affects lpf2 directly). Above is with default sampling frequency : 12.5 with 26, I get also two bad values, but different from the previous ones : Proceeding without activating any channels -0.242811 -1.215279 0.709155 -0.055539 -1.216197 0.466650 0.002142 -0.075582 0.034578 0.002142 -0.075123 0.035955 0.002295 -0.075582 0.036261 0.002142 -0.075429 0.035955 with 52, I now get more bad values : Proceeding without activating any channels -0.267750 -0.745569 0.558909 -0.486999 -3.376863 1.719567 0.130815 -0.705942 0.054315 0.001989 -0.075582 0.036414 0.001224 -0.075123 0.035955 0.001836 -0.075888 0.036108 0.002448 -0.075582 0.036261 0.002295 -0.075888 0.035190 0.002295 -0.075888 0.036261 0.002907 -0.075888 0.036261 with 106, I get evenmore bad values Proceeding without activating any channels -0.024174 -0.082773 -0.154377 -0.412335 -0.387702 0.665856 -0.450432 -2.840751 1.692486 -1.784439 -4.931190 4.186539 -1.090125 -4.231215 2.580345 0.674730 -3.370896 0.127908 0.562275 -2.838456 0.115209 0.085680 -0.486846 0.045900 0.003825 -0.081702 0.040392 0.004437 -0.078030 0.037179 0.004284 -0.076806 0.036261 0.003213 -0.075735 0.035343 0.003672 -0.075735 0.035343 0.002295 -0.074970 0.036567 0.002448 -0.076041 0.037179 0.002448 -0.076347 0.037179 0.002142 -0.076347 0.037332 0.001989 -0.076194 0.036108 0.001989 -0.076194 0.035955 0.002142 -0.075276 0.036106 Philippe
